Generation Of Active Oxygen Radicals Research Articles

Содержание фенольных соединений в лишайниках в зонах тектонических разломов

The paper studies the influence of geoecological factors on the content of phenolic compounds (PCs) in lichens of the genus Cladonia in the Velsko-Ustyansky and Kholmogorsky tectonic knots (TKs). Lichens were sampled from the test plots (TPs) laid out in the center of the knots and outside the knots (control). The geochemical situation, soil-climatic and environmental conditions in the zone of TKs influence the lichens chemical composition. It is found that the ash content of lichens growing in the center of the TK is 1.8–2.3 times higher than in the control, which indicates a significant accumulation of lithogenic elements in the lichen thallus in the tectonic fault zone. Lichens are exposed to multifactorial adverse effects (increased radiation background and heat flux, electromagnetic radiation, electric and magnetic fields, etc.) in the territory of TKs. This provokes excessive generation of active oxygen radicals and contributes to the rearrangement of lichen metabolism, changing the dynamics of accumulation of PCs and their biosynthesis. The content of the water-insoluble fraction of PCs in lichens was found to increase from the control point to the center of the TK, while the relative share of the water-soluble fraction of PCs in the total composition decreases. This is probably due to an increase in oxidative processes and a decrease in reductive processes in lichens under adverse conditions. The paper shows that the biosynthesis of PCs in lichens is most active in the spring-summer (April and July) vegetation period. The impact of geoecological factors enhances the biosynthesis of secondary metabolites of phenolic nature in lichens in the conditions of the TKs: usnic acid (UA) and atranorin. The content of UA in the composition of the water-insoluble fraction of PCs in lichens growing in the center of the TK is 1.5–1.7 times higher during the spring-summer vegetation period than in lichens growing outside the TK. The quantitative distribution of the water-insoluble fraction of PCs depends on the lichen thallus part and has a gradient character. Their content in the upper growing parts of lichens growing in the center of the TK and in the control is 2 and 1.7 times higher than in the old zones, respectively. Thus, PCs in lichens are active metabolites and their content in thallus can serve as a biomarker of the state of the environment.

Paper-based Chemiluminescence Device with Co-Fe Nanocubes for Sensitive Detection of Caffeic Acid.

In this work, a new chemiluminescence (CL) system of Co-Fe prussian blue analogs nanocubes (Co-Fe PBA NCs) that can catalyze luminol to produce strong CL in the absence of H2O2 was established. Co-Fe PBA NCs have the property of oxidase-like activity, and it can catalyze the generation of active oxygen radicals in a dissolved oxygen system. Since caffeic acid (CA) can remove reactive oxygen species in the system, a sensitive detection method for CA on a paper-based chip was developed. Under the optimal conditions, this method showed a good linear response to CA in the range of 10 - 800 ng mL-1 with a limit of 3 ng mL-1. The proposed method had been used for the determination of CA in tea samples. The results may open a new avenue for the catalytic property on luminol CL system without extra oxidants.

Influence of tectonic faults on the conditions and properties of some components of a biogeocenosis in a subarctic area

In geoecology, the nature of the effect of tectonic faults on the environment is not well studied. The influence of natural landscapegeochemicalfactors on the state and properties of some components of biota of different hierarchical levels is studied at the intersection oftwo tectonic faults (Velsko-Ust’yanskiy tectonic knot (TK)) in the Arkhangelsk region. Two species of shrubby lichens (Cladonia stellaris Opiz.and Usnea subfloridana Stirt.) and woody plants (spruce – Picea abies L. and Scots pine – Pinus sylvestris L.) were chosen as test systems. Thefield studies were carried out at nine test sites (in the centre, on the periphery and some distance from TK – the background reference point)in different types of forest. The ash content of samples of the lichen Cladonia growing in the centre of the TK (1.12–1.22%) is double that in thecontrol area (0.56–0.58%), and for the lichen Usnea, it is seven times higher (6.82–6.99% at the centre and 0.97–1.09% in the control area). Theash content of tree bark collected at the centre of TK (1.27–1.29%) is double that at the control site (0.56–0.76%). This indicates a significantaccumulation of metals in the vegetation in the TK zone. The accumulation of heavy metals, the low water content of plants, the influenceof geomagnetic fields and other factors provoke excessive generation of active oxygen radicals and plants have various physiological,biochemical and morpho-biometric means of combating their adverse effects. The synergism of the cooperative protective action of lichenmatrix components on oxidative stress is expressed in terms of changes in biochemical parameters. At the centre of the TK, the lichenscontains up to 190 μg g−1 of ascorbic acid, whereas in the control area it does not exceed 130 μg g−1. The content of usninic acid in thecentre is 1.5–2 times higher for the Usnea subfloridana and is 1.5 times higher for Cladonia stellaris compared to the level in the control area.

Hepatobiliary parasites

Although a number of human parasites can occasionally be found in the liver and/or biliary ducts, there are some that are more commonly found in these body sites including: <i>Leishmania</i> spp., micro-sporidia, <i>Cryptosporidium</i> spp., and several trematodes (<i>Clonorchis, Opisthorchis</i>, and <i>Fasciola</i> spp.), the most important group. The liver trematodes are food borne; it is estimated that >50 million people are infected with >750 million at risk. Public health concerns include cholangiocarcinoma (<i>Clonorchis, Opisthorchis</i>) and severe liver disease (<i>Fasciola</i>). Diagnosis is usually confirmed by fecal examinations, while cholangiography, ultrasonography, and liver scans may reveal lesions consistent with liver fluke infection. Pathological changes (<i>Clonorchis, Opisthorchis</i>) are confined mainly to the biliary tree and morbidity is associated with the worm burden of the host. Chronic inflammatory processes, generation of active oxygen radicals, altered cellular detoxification mechanisms, activation of oncogenes, functional loss of tumour-suppressor genes and dysregulation of cell proliferation and apop-totic mechanisms have been identified as important contributors in the development of cholangiocarcinomas. In <i>Fasciola</i> infections, pathology depends on the number of flukes penetrating the liver. There may be hyperplasia of the biliary epithelium and fibrosis of the ducts with portal or total biliary obstruction. The gallbladder undergoes the same types of changes.

Maximum Incorporation of Oxygen Radicals, O- and O2-, into 12CaO·7Al2O3 with a Nanoporous Structure

The effects of oxygen partial pressure (p o2 ) up to 400 atm on the generation of active oxygen radicals in 12CaO.7Al 2 O 3 (C12A7) was examined using a hot isostatic pressing technique. Concentrations of superoxide (O 2 -) and oxygen anion radicals (O - ), which were analyzed from a combination of electron paramagnetic spin resonance (EPR) and Raman spectroscopy, increased with p o2. The total concentration of the radicals reached 1.7 x 10 21 cm 3 , which is comparable to the theoretical maximum, confirmed that dominant radical incorporation process is O 2- (cage) + O 2 (atmosphere) O - (cage) + O 2 - (cage). The radical incorporated C12A7 has a large magnetic susceptibility that obeys Curie's law down to 2.5 K without magnetic ordering, although a weak exchange interaction was suggested by the line narrowing of the EPR signal.

ESR spin-trapping detection of radical intermediates in the TiO 2-assisted photo-oxidation of sulforhodamine B under visible irradiation

The ESR spin-trapping technique using 5,5-dimethyl-1-pyrroline- N-oxide (DMPO) and N- t-butyl-α-phenyl-nitrone (PBN) as spin-trap reagents has been applied to detect free radical intermediates generated during the in situ visible irradiation of aqueous sulforhodamine B (SRB)–TiO 2 air-saturated dispersion. Hydroxyl radical ( OH), hydroperoxyl radical (HO 2 ) and hydrated electrons (e aq −) were detected in the TiO 2-assisted photo-oxidation of SRB under visible irradiation. The mechanism for the generation of active oxygen radicals and the role of these photogenerated active oxygen radicals in the photo-oxidation process are discussed. It is suggested that the oxygen molecules rather than these active oxygen radicals are the main oxidizing agent and play an important role in the visible photo-oxidation of SRB mediated by TiO 2 particles.

DNA breaking activity and mutagenicity of soy sauce: characterization of the active components and identification of [formula omitted

Soy sauce is a seasoning consumed widely in Southeast Asia. When supercoiled was incubated with soy sauce at pH 7.4 and 37°C, extensive breaking of DNA single-strands was caused. It was found that the breaking activity was due to multiple components with different molecular weight and polarity. One of the components with the breaking activity was purified successively by extraction with ethyl acetate, thin-layer chromatography and high performance liquid chromatography, and identified as 4- hydroxy-5- methyl-3(2H)- furanone (HMF), one of the fragrant components in soy sauce. Formation of this component was found due to Maillard reaction of pentoses/amino acids. HMF was readily degraded into the compound with an endiol-ketol structure and reducing activity. Using 5,5-dimethyl-1-pyrroline N- oxide (DMPO) in an electron spin resonance-spin trapping technique, generation of hydroxyl radical in an aqueous solution of HMF was confirmed. While DNA breaking by soy sauce was little inhibited by the scavengers of active oxygen radicals, the breaking by HMF was effectively inhibited by superoxide dismutase, catalase, hydroxyl radical scavengers, spin-trapping agents, thiol compounds and metal chelating agents. Hence, DNA breaking activity of HMF was found due to generation of active oxygen radicals. HMF was found mutagenic to Salmonella bacteria without metabolic activation, probably due to generation of active oxygen radicals.

Absence of generation of active oxygen radicals coupled with phagocytosis by the hemocytes of the clam, Ruditapes decussatus (Mollusca: Bivalvia)

The production of oxygen radicals by hemocytes of Ruditapes decussatus as a cytotoxic mechanism associated with phagocytosis was studied. In vitro phagocytosis assays of yeast cells (zymosan) by clam hemocytes were performed. Two different methods for oxygen radical detection were tested, based on the technique of luminol-dependent chemiluminescence and on the reduction of nitroblue tetrazolium. Hemocytes of the Pacific oyster, Crassostrea gigas , were used as positive control in the assays, because of their ability to produce oxygen radicals. The results obtained showed that the hemocytes of R. decussatus were not able to produce toxic oxygen radicals during phagocytosis, irrespective of whether yeast cells were opsonized or not. Similar results were obtained with hemocytes of the cockle, Cerastoderma edule .

ESR Spin-Trapping Study of Active Oxygen Radicals from Photoexcited Semiconductors in Aqueous H2O2 Solutions

Abstract Experiments were carried out concerning the relation between the production of active oxygen radicals from three semiconductors [TiO2 (anatase and rutile) and WO3] and the concentration of H2O2 by the ESR spin-trapping technique using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap. Two natures of hydroxyl radicals were produced from photoexcited semiconductors in aqueous H2O2 solutions. These originated in the reduction of H2O2 and the oxidation of water, which were confirmed using 17O-labeled water. The mechanism for the generation of active oxygen radicals is discussed regarding the energy band structures of the semiconductors, the redox potentials of the oxygen radicals, and the surface acidity and basicity of semiconductors.

ESR Study of Active Oxygen Radicals from Photoexcited Semiconductors Using the Spin-Trapping Technique

Abstract The ESR spin-trapping technique was used to detect active oxygen radicals by photoexcitation of powdery semiconductors (TiO2, WO3, CdS, and Fe2O3) in water and aqueous H2O2 solutions using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as spin trap. Superoxide ion (O2−), hydroperoxyl radical (·O2H) and hydroxyl radical (·OH) were detected under photoexcitation. The mechanism for the generation of active oxygen radicals is discussed referring to the energy band structures of the semiconductors and the redox potentials of the oxygen radicals.

Synergistic interactions between nadph-cytochrome P-450 reductase, paraquat, and iron in the generation of active oxygen radicals

The toxicity associated with paraquat is believed to involve the generation of active oxygen radicals and the production of oxidative stress. Paraquat can be reduced by NADPH-cytochrome P-450 reductase to the paraquat radical; this results in consumption of NADPH. A variety of ferric complexes, including ferric-ATP, -citrate, -EDTA, ferric diethylenetriamine pentaacetic acid and ferric ammonium sulfate, produced a synergistic increase in the paraquat-mediated oxidation of NADPH. This synergism could be observed with very low concentrations of iron, e.g. 0.25 μM ferric-ATP. Very low rates of hydroxyl radical were generated by the reductase with paraquat alone, or with ferric-citrate or -ATP or ferric ammonium sulfate in the absence of paraquat; however, synergistic increases in the rate of hydroxyl radical generation occurred when these ferric complexes were added together with paraquat. Ferric-EDTA and -DTPA catalyzed some production of hydroxyl radicals, which was also synergistically elevated in the presence of paraquat. Ferric desferrioxamine was essentially inert in the absence or presence of paraquat. This enhancement of hydroxyl radical generation was sensitive to catalase and competitive scavengers but not to superoxide dismutase. The interaction of paraquat with NADPH-cytochrome P-450 reductase and ferric complexes resulted in an increase in oxygen radical generation, and various ferric complexes increased the catalytic effectiveness and potentiated significantly the toxicity of paraquat via this synergistic increase in oxygen radical generation by the reductase.

Flow cytometric analysis of oxidase activity of neutrophils from chronic granulomatous disease patients.

Phagocyte cells, neutrophils and macrophages constitute the main defense mechanisms of the human body against invading microorganisms. The bactericidal activity of polymorphonuclear leukocytes (PMNs) involves the activation of a cell membrane associated NADPH oxidase enzyme“. Following activation of the NADPH oxidase enzyme, a cascade of oxidation/reduction reactions occurs, with the generation of several oxygen radicals. Superoxide (0 2 − ) hydrogen peroxide (H202), hydroxyl radical (HO) singlet oxygen (0) are the main oxygen by-products of the respiratory burst of PMNs2 and have an important role in killing of bacteria. The enzyme NADPH oxidase has a major function in the generation of O 2 − radical while other enzymes including superoxide dismutase3, myeloperoxidase4, catalase and glutathione peroxidase5 serve a regulatory activity in the respiratory burst. NADPH oxidase differs from other cellular oxidase enzymes (i.e., mitochondrial), since it is a cyanide insensitive enzyme6. The activation of the NADPH oxidase enzyme with different soluble stimulants as phorbol esters7, formyl-methionyl-leucyl-phenylalanine8 and γ-hexachlorocyclohexane9 results in the generation of active oxygen radicals and mimics the biochemical events which occur during phagocytosis in vivo.

Modulation of synaptic GABA receptor binding by membrane phospholipids: Possible role of active oxygen radicals

Pretreatment of cerebral synaptic membrane preparations with phospholipase (PLase) A 2 invariably induced a significant enhancement of [ 3H]muscimol binding in a dose-dependent manner iwth a concomitant elevation of the content of total free fatty acids in the membrane. In vitro addition of various free fatty acids exhibited no profound alteration in [ 3H]muscimol binding, whereas a significant enhancement of the binding was induced by the pretreatment of the membrane with unsaturated free fatty acids such as arachidonic acid and linoleic acid, but not by that with saturated free fatty acids. None of the inhibitors of arachidonic acid metabolism including indomethacin (an inhibitor of cyclo-oxygenase) and nordihydroguaiaretic acid (an inhibitor of lipoxygenase), however, had a significant preventive action on the augmentation of [ 3H]muscimol binding. On the other hand, various scavengers for superoxide anion radical such as superoxide dismutase, tiron and nitroblue tetrazolium (NBT) not only suppressed the PLase A 2-induced enhancement of [ 3H]muscimol binding, but also diminished the augmentation of the binding due to PLase C and arachidonic acid. It was also found that a remarkable facilitation of the formation of superoxide anion radical was induced by the treatment of synaptic membrane with PLase A 2, PLase C and arachidonic acid, all of which exhibited a prominent stimulation of the binding. In addition, treatment of the membrane with xanthine and xanthine oxidase, a superoxide anion radical generating system, resulted in a profound stimulation of the binding. The PLase A 2-induced enhancement of the binding was also attenuated by the scavengers for hydrogen peroxide like catalase as well as by those for hydroxyl radical such as dimethylnitrosoaniline, mannitol, methanol and ethanol, but not by those for singlet oxygen radical including α-tocopherol and β-carotene. The present results that membrane phospholipids may play an important role in the modulation of the association of GABA with its relevant receptor through the generation of active oxygen radicals from unsaturated free fatty acids which are yielded by the catalytic action of PLase A 2 and/or PLase C.